The order in which the following oxides are arranged according to decreasing basic nature is
Na2O, MgO, Al2O3, CuO
MgO, Al2O3, CuO, Na2O
Al2O3, MgO, CuO, Na2O
CuO, Na2O, MgO, Al2O3
More the metallic character higher the e− donating tendency. Therefore lower the I.E. more the basic nature of oxide.